FOR DISTINGUISHING SACCHARINE JUICES. 599 



Article II. — Utility of the Optical Character for estimating the 

 Changes which may occur in determinate Species mingled together. 



27. It would be important to ascertain the influence that chemical 

 species, the relations of which to the property of which I am treating 

 have been previously perfectly determined, would exercise by their 

 mutual contact, whether in the destruction or the neutralization of this 

 property, in its development, augmentation, or diminution. I conceive 

 that there are mutual actions of certain bodies in solution of which we 

 are at present ignorant, in consequence of not possessing means of 

 observing some phaenomenon which is only manifested when they are 

 mutually present. It is, I apprehend, particularly in relation to the or- 

 ganoleptic properties of bodies that it would be useful to attempt re- 

 searches of this nature. I cannot here enter upon the subject more in 

 detail ; but I reserve the particulars for a work upon the neutrality of 

 bodies, considered in the most general manner. 



Article III Utility of the Optical Character as a Reagent in the 



Determination of Chemical Species of Organic Origin. 



28. A certain vegetable fluid, or liquid of animal origin, or in a word 

 any solution the nature of which is investigated by analysis, when sub- 

 mitted to the action of polarized light, gives a determinate result. Well! 

 I apprehend that the observation of the optical property may furnish 

 useful indications in the folloAving cases : 



First case: 



29. In which the properties of the substance analysed are found in 

 the separate principles. The optical property of these principles ex- 

 plains perfectly that of the substance of which they are the consti- 

 tuents ; consequently this result concurs with other observations to 

 prove that it has not sustained alteration in the analysis. 



Second case : 



30. In which all the properties of the substance analysed are not 

 found in the separate principles. The observation of the optical cha- 

 racter may here assist in the solution of the question. Has there been 

 any alteration of the separated principles ? or do not the changes ob- 

 served arise from the destruction either of a combination or a mutual 

 influence of principles, while no alteration has occurred in the ele- 

 mentary composition of these principles? We then enter upon the ques- 

 tion which I have considered in my " Considerations generales sur 

 V Analyse organique." p. 116. 



31. I think that sufficient attention has not been given to ascertain 

 whether there be not in grape juice and sugar of starch of the first 

 formation some body foreign to grape sugar and sugar of starch, 



